The appearance of a roasted and ground coffee product is usually considered by the consumer in his evaluation of the coffee product. Some comsumers are known to prefer a roasted and ground coffee product which has a non-homogeneous or speckled color appearance. Some of these consumers also prefer a roasted and ground coffee product that also has a distinctly non-homogeneous particle size distribution.
It is of course recognized that passing whole roasted coffee beans through a commercial coffee mill does not produce all uniformly sized particles but rather yields a particle size distribution which generally approximates a bell-shaped curve. However, the particle size character of coffee products which are prepared by grinding a blend of whole roasted coffee beans is generally regarded as uniform. For the purpose of this invention, a non-homogeneous or non-uniform particle size distribution will be a product which has a plurality preferably two of roast color fractions with the average particle size of two different fractions differing by more than 300 microns. Preferably the average particle size difference will be at least 500 microns.
It is of course possible to separately grind different fractions of whole roasted coffee beans to two or more distinct particle sizes, and this type of procedure is disclosed in U.S. Pat. No. 3,544,331 to Hair. Separate grinding, however, involves duplicative processing steps and probably duplicative grinding equipment, and this procedure could prove to be unfeasible or economically prohibitive in some existing coffee roasting facilities. It would therefore be desirable to produce a non-uniform particle size distribution without adding additional processing steps or equipment.
Conventional practice for using separately roasted and quenched coffees have heretofore either combined the roasted beans prior to grinding or else separately ground the roasted beans and combined the ground coffee. In those cases where the roasted coffee fractions are combined prior to grinding, the roasted coffee beans have heretofore contained comparable levels of moisture and the resulting product has a uniform particle size distribution among the fractions. In those cases where the roasted coffee fractions are combined after grinding, it is known, as shown in the aforementioned Hair patent, to produce non-uniform particle size distributions.
Although high moisture levels have previously been disclosed (U.S. Pat. No. 3,482,987) for use in quenching lower grade roasted coffees, this patent discloses that these high-moisture beans must be dried prior to use in a roasted and ground coffee product.